Pressure sensors have been developed that can resolve pressure differences in the surrounding environment of around 1.5 Pascal (Pa). These sensors have a sensitivity enabling applications for determining differences in altitude of less than 1 meter from measurements of the air pressure. This makes them fit for detecting motion of a person wearing such a pressure sensor. In EP1642248 a pressure sensor is attached to a person and used to determine height change. The determined height change is indicative of the fall of the person.
WO2009/101566 discloses that the altitude measurement provided by such a pressure sensor has a possible error of about 0.5 meter, whereby this error depends on the orientation of said pressure sensor.
For a fall detector it is preferable that also small height changes are detectable. For example when a person falls out of his chair the possible error in the measurement of a pressure sensor may be in the order of the height change that is to be detected.